Computed Tomography-Verified Pacing Location of Micra Leadless Pacemakers and Characteristics of Paced Electrocardiograms in Bradycardia Patients

Abstract

Introduction

The leadless pacemakers are implanted routinely under fluoroscopic image, yet the pacing sites and corresponding paced electrocardiography (ECG) remain unclear. This study was to determine the computed tomography (CT)-verified location of the leadless Micra pacemakers (Micra) and ECG characteristics.

Methods

Twenty consecutive patients who met the pacemaker indications for bradycardia and underwent fluoroscopy assisted Micra implantation were enrolled. All subjects underwent a postoperative CT scan to determine the precise location of the Micra pacing tip. Paced 12-lead ECG characteristics were analysed and correlated with the Micra tip location.

Results

In the nine partitions of fluoroscopic RAO images, 14 (70%) of 20 patients had the Micra tip in zone 5, 5 (25%) in zone 6 and 1 in zone 2. Reconstructed CT 3-D cardiac images found Micra tips mostly clustered near the anterior insertion between the RV septum and free wall with 12 cases at the insertion-septal side and 8 at the free-wall side. ECG morphological analysis found that the peak deflection index in ECG lead V1 was 0.409 ± 0.058 for Micra tips at the insertion-septal side and 0.527 ± 0.062 in the free-wall side (p < 0.001 between two sides) and R wave amplitude in lead V6 appeared larger for Micra tips in the free-wall group compared to Micra tips in the insertion-septal group, while there was no difference in QRS duration between two sides.

Conclusion

In routine Micra implantation, the pacing sites were often located in the anterior insertion region.